Spring brake cylinder having an emergency release device

ABSTRACT

In order to achieve, in the case of a spring brake cylinder having an emergency release device, particularly for rail vehicles, and having a spring piston ( 8 ) which can be moved axially within a housing ( 1 ) and which, on the one hand, can be moved by means of an accumulator-type spring ( 9 ) for operating the brake in the event of a pressure drop and, on the other hand, can be moved by a spring pressure chamber ( 10 ), which can be acted upon by a pressure medium, for releasing this spring brake, as well as having a normally locked, not self-locking threaded screw drive ( 12 ) which is arranged in the flux of force between the spring piston ( 8 ) and an output-side piston rod ( 5 ) and which can be manually unlocked by way of a latch ( 13 ) assigned to the emergency release device, in order to be able to release the spring brake without any pressure medium, a reliable functioning of this emergency brake device in a simple manner, it is suggested that an outer-radial sliding surface ( 19 ) for the latch ( 13 ) held in contact thereon is assigned to the part of the threaded screw drive ( 12 ) which is rotatable relative to the housing ( 1 ), on which sliding surface ( 19 ) only a detent flank ( 22 ) interacting in a form-locking manner with the latch ( 13 ) is constructed for locking the emergency release device, the pitch of the threaded screw drive ( 12 ) being dimensioned such that the rotatable part of the threaded screw drive ( 12 ) carries out less than a complete rotation along its maximal axial adjusting stroke.

[0001] The invention relates to a spring brake cylinder, particularly for rail vehicles, having an emergency release device and having a spring piston which can be moved axially within a housing and which, on the one hand, can be moved by means of an accumulator-type spring for operating the brake in the event of a pressure drop and, on the other hand, can be moved by a spring pressure chamber, which can be acted upon by a pressure medium, for releasing this spring brake, as well as having a normally locked, not self-locking threaded screw drive which is arranged in a flux of force between the spring piston and an output-side piston rod and which can be manually unlocked by way of a latch assigned to the emergency release device, in order to be able to release the spring brake without any pressure medium.

[0002] As a safety-relevant subassembly, spring brake cylinders of the above-described type are preferably used in rail vehicle construction for ensuring a brake operation when there is no brake pressure. In the case of a spring brake cylinder, the brake can be operated only by way of the accumulator-type spring so that the spring brake cylinder can be used as a parking brake of a rail vehicle in the parked condition and as a safety brake when the compressed-air system is leaking or has failed during the driving operation.

[0003] A spring brake cylinder of the above-mentioned type is known from German Patent Document DE-OS 26 08 502. The spring brake cylinder consists essentially of a cylindrical housing with an interior accumulator-type spring which, for the brake operation, in the event of a pressure falling in the pressure chamber, acts upon the piston from the opposite side, so that the output-side piston rod moves out. A releasing of the brake takes place by the admission of pressure medium to the pressure chamber, in which case the accumulator-type spring is tensioned again and the piston rod moves in.

[0004] Furthermore, the spring brake cylinder has an emergency release device for the interruption of and the automatic returning into the above-explained normal operating mode of the spring brake cylinder, for the purpose of which a lockable, not self-locking threaded screw drive arranged in the flow of force between the piston and the piston rod is locked or unlocked. The threaded screw drive consists essentially of a part which is rotatable with respect to the housing and of a part which is non-rotatable. The rotatable part may either be a nut which interacts with the piston and which is in a threaded engagement with a screw constructed on the piston rod; (or ? translator) the spindle may be constructed as the rotatable part which will then be rotatably disposed with respect to the piston rod, in which case its assigned nut is non-rotatably arranged with respect to the piston. Both principles carry out the same function.

[0005] During the normal braking operation—that is, when pressure is present—, the rotatable part of the threaded spindle drive is locked by way of a latch, so that a rigid flux of force is established between the piston and the piston rod in order to permit a pressure-medium-operated restoring of the piston while tensioning the accumulator-type spring in the above-described manner. The emergency release device is required in the event that no pressure is available for the compression of the accumulator-type spring and therefore for releasing the brake, but the rail vehicle has to be moved—for example, during a switching. In this case, the transmission of force from the piston to the piston rod is manually interrupted from the outside by the unlocking of the not self-locking threaded screw drive by way of the latch, whereby a release of the brakes can take place without any pressure. The return into the original operating condition of the spring brake cylinder takes place automatically when pressure is available again which then, as a result of the compression of the accumulator-type spring, causes a return movement of the parts of the emergency release device.

[0006] In the prior art, this function is implemented by way of a detent pawl toothing provided at the outer radius on the rotatable part of the threaded screw drive, which detent pawl toothing meshes with the latch in the manner of a ratchet and pawl. The detent pawl toothing permits a relative rotating movement of the rotatable part of the threaded screw drive in only one direction, whereas the rotation into the other direction is prevented by the detent flanks of the toothing.

[0007] Here, the problem arises that, if the latching engages before the stoppage of the rotating parts, particularly, during a brief operation as the result of a slipping off the handle of the latch, the ratchet and pawl may be considerably worn and damaged. At an extremely low temperatures, particularly as a result of the then reduced viscosity of the lubricant, the end position in the emergency-released condition may not be reliably reached so that the brake cannot be completely released. This unfavorable condition will then be fixed by a reengagement of the latch. In addition, the forming of the detent pawl toothing at the rotatable part of the threaded screw drive requires fairly high expenditures with respect to the manufacturing.

[0008] It is therefore an object of the present invention to further improve a spring brake cylinder of the above-described type such that a reliable functioning of the emergency release device is achieved in a simple manner.

[0009] Based on a spring brake cylinder according to the preamble of claim 1, this object is achieved in connection with its characterizing features. The dependent claims, which follow, indicate advantageous further developments of the invention.

[0010] The invention includes the technical teaching that an outer-radial sliding surface for the latch held in contact thereon is assigned to the part of the threaded screw drive which is rotatable relative to the housing, on which sliding surface a detent flank interacting in a form-locking manner with the latch is constructed for locking the emergency release device. The pitch of the threaded screw drive is dimensioned such that the rotatable part of the threaded screw drive carries out less than a complete rotation along its maximal axial adjusting stroke.

[0011] The advantage of the invention is particularly that, as a result of the avoidance of a plurality of teeth on the ratchet, a wearing of the toothing as a result of an unfavorable engagement situation of the latch during the movement of the rotatable part of the threaded screw drive is avoided. In the event of a brief operation as a result of a slipping off the handle of the latch, the latch always comes to rest on the sliding surface. A skipping of a tooth by the latch, which would cause damage, is made impossible in that the rotatable part of the threaded screw drive can maximally carry out only one complete rotation. The engaging position of the latch is therefore precisely defined. This position is exclusively located in the end position of the piston after a restoring of the operability from the emergency-released condition of the spring brake cylinder.

[0012] Advantageously, the sliding surface of the part of the threaded screw drive which can be rotated relative to the housing is constructed in the manner of a curved path. In this case, the detent flank constructed on the curved-path-type sliding surface preferably has an essentially radially aligned surface in order to ensure a secure engagement of the latch. The curved-path-type further development of the sliding surface has the advantage that the stroke difference which occurs here in an interaction with the latch can be utilized for indicating the switching condition of the emergency release device. The curved path may be provided with additional shaped-on sections or indentations in order to be able to judge from the outside in a simple manner by way of different resulting stroke differences, for example, in the emergency-released condition, the degree of the release of the brake.

[0013] Within the scope of the present invention, the detent flank constructed on the sliding surface can be shaped in a groove-type manner as an indentation or in a tooth-type manner as an elevation or in another shape permitting a detent engagement with the latch.

[0014] The emergency release device constructed according to the invention permits a use in the case of spring brake cylinders with a part of the threaded screw drive which can be rotated relative to the housing and which is constructed as a screw which can be axially displaced together with the piston rod, which screw is disposed to be rotatable about the piston rod, in this case the screw interacting with a nut, as the non-rotatable part, of the threaded screw drive which is stationarily arranged with respect to the spring piston.

[0015] As an alternative thereto, a use is also possible in the case of spring brake cylinders, where the part of the threaded screw drive rotatable relative to the housing is constructed as a nut which is axially displaceable together with the spring piston and which is coaxially rotatably disposed on the spring piston, and which interacts with a screw of the threaded screw drive, as a non-rotatable part, which is stationarily arranged with respect to the piston rod.

[0016] In the former case of a rotatable screw, a gear wheel element, which has the outer-radial sliding surface with the detent flank according to the invention, can be stationarily fastened at the end side to the screw as a separate component. On the whole, the manufacturing of the rotatable screw is simplified thereby and a separate exchange of a worn component can take place by demounting.

[0017] A spring arranged between the latch and the housing is preferably provided in order to hold, in the manner of a compression or tension spring, the latch in a continuous contact on the sliding surface of the rotatable part of the threaded screw drive. In addition to a manual operation, it is conceivable to operate the latch against the spring force also by means of an auxiliary device in a remote-controllable manner. As the auxiliary device, a switch-controlled electric or pneumatic actuator could be used in which case the auxiliary energy required for this purpose may optionally be made available by storage in a battery or a pressure reservoir.

[0018] Additional measures improving the invention are indicated in the dependent claims or are described in detail in the following by means of figures together with the description of a preferred embodiment of the invention.

[0019]FIG. 1 is a longitudinal sectional view of a spring brake cylinder having an emergency release device according to the present invention;

[0020]FIG. 2a is a top view of a schematic representation of a ratchet according to the invention in the operative condition;

[0021]FIG. 2b is a lateral view of the ratchet according to FIG. 2a;

[0022]FIG. 3a is a top view of a schematic representation of a ratchet according to the invention in the emergency-released condition; and

[0023]FIG. 3b is a lateral view of the ratchet according to FIG. 3a.

[0024] The spring brake cylinder according to FIG. 1 consists essentially of a two-piece, essentially cylindrical housing 1 which, within a first half, contains an axially displaceable service brake piston 2 which, by way of an assigned service brake pressure chamber 3, can be acted upon by a pressure medium by the connection 4 arranged at the housing 4, in order to transmit, by way of a piston rod 5 extending out of the housing 1 in a sealed manner and fastened coaxially to the service brake piston 2, a braking force to a brake linkage (not shown here in detail) of a rail vehicle. The restoring of the service brake piston 2 takes place in the bled condition of the service brake pressure chamber 3 essentially by way of the effect of the force of a restoring spring 6 acting between the housing 1 and the service brake piston 2. Furthermore, the piston rod 5 is equipped with a mechanical adjusting device 7 for compensating a wear tolerance resulting from the wear of the brake linings.

[0025] In addition to the above-described service brake, a spring brake is also integrated in the spring brake cylinder, for the purpose of which an axially movable spring piston 8 is arranged within the second half of the housing 1. On the one side, the spring piston 8 can be moved by several accumulator-type springs 9 which are arranged at the same radial distances and at mutually the same distances with respect to the spring piston 8 and, on the other side interact with parts of the housing 1 in order to automatically operate the brake at a significant pressure drop. On the other side of the spring piston 8, a spring pressure chamber 10 is situated. The spring pressure chamber 10 has an assigned connection 11 and can be acted upon by pressure medium for releasing the spring brake, thus for restoring the spring piston 8 against the force exercised by the accumulator-type spring.

[0026] In the flux of force between the spring piston 8 and the output-side piston rod 5, a not self-locking threaded screw drive 12 is arranged which is locked during the normal operation and which can be manually unlocked by means of a latch 13 assigned to the emergency release device, in order to be able to release the spring brake without any pressure medium.

[0027] The part of the threaded screw drive 12 which is rotatable relative to the housing 1 is constructed as a screw 14 which is axially displaceable together with the piston rod 5 and which is disposed to be rotatable about the piston rod 5. The screw 14 can be displaceably by way of an outer-radial plastic bush 15 and rotatably guided in the housing 1.

[0028] A nut 16, as a non-rotatable part of the threaded spindle drive 12, arranged stationarily with respect to the spring piston 8 interacts with the screw 14. A rotating movement of the spring piston 8 with the nut 16 is prevented in this case by a torque lock 17 which interacts with parts of the housing 1 in the manner of a mechanical stop.

[0029] For locking and unlocking the threaded screw drive 12, a gear wheel element 18 is provided which is stationarily but demountably fastened to the screw 14. The gear wheel element 18 has an outer-radial sliding surface with a detent flank (which will be explained later) for the latch 13 interacting therewith for forming the emergency release device. Between the lock 13 and the housing 1, a spring 20 is arranged which is constructed in the manner of a compression spring in order to hold the latch 13 in a continuous contact on the sliding surface 19 of the gear wheel element 18. By way of an exterior grip 21, the latch 13 can be manually lifted off the sliding surface 19 against the force of the spring 21.

[0030] In the illustrated position, the spring brake cylinder is in the emergency-released condition. In this case, the spring brake was released without any pressure medium by pulling on the latch 13, which discontinues the form-locking engagement on the gear wheel element 18. As a result of the thereby implemented unlocking of the threaded screw drive 12, the screw 14 is freely rotatable so that, as a result of restoring forces, which, among other things, originate from the return spring 6, an axial moving-in movement is caused of the piston rod 3 connected with the screw 14 for releasing the brake. In this case, the pitch of the threaded screw drive is dimensioned such that the screw 14 with the gear wheel element 18 carries out less than an entire rotation along its maximal axial adjusting stroke.

[0031] According to an individual representation according to FIG. 2a, the form-locking engagement of the latch 13 on the gear wheel element 18 takes place on a single detent flank 22 constructed to be radially oriented thereon, so that the threaded screw drive 12 is locked. The remaining circumferential surface of the gear wheel element 18 is constructed here as a uniform curved path 19. In the illustrated locked condition, the gear wheel element 18—as illustrated in FIG. 2b—is in an axial end position in which a form-locking interaction with the latch 13 is still ensured. In this locked condition, a normal braking operation can take place, in which case an axial displacement occurs between the stationary latch 13 and the axially movable gear wheel element 18 during a stroke movement of the piston rod 5.

[0032] In the emergency-released condition illustrated in FIG. 3a, the form-locking engagement is discontinued between the latch 13 and the gear wheel element 18. The threaded screw drive 12 is unlocked in this case, and the latch 13 can slide freely along the curved path 19. After the unlocking, an axial relative movement takes place between the latch 13 and the gear wheel element 18, originating from the end position illustrated in FIG. 3b into the end position illustrated in FIG. 2b because of the axial moving-in movement of the piston rod 5 together with the screw 14. For again establishing the readiness, when a pressure medium is available again, a release stroke of the spring piston 8 is automatically carried out while the accumulator-type springs 9 are compressed, in which case a rotating back of the unlocked screw 14 with the gear wheel 19 fastened thereon takes place until the latch 13 arrives again in a form-locking engagement with the detent flank 22 and thus the locked condition of the threaded spindle drive 12 is reestablished. A normal braking operation will now be possible again.

[0033] The invention is not limited to the above-described preferred embodiment. On the contrary, modifications thereof are conceivable which, despite a different construction, extend into the scope defined by the claims, In particular, the invention is not limited to an embodiment with a rotatable screw and a nut which is non-rotatable with respect thereto. A use is also conceivable in the case of a reverse principle of a rotatable nut with respect to a non-rotatable screw.

LIST OF REFERENCE NUMBERS

[0034]1 housing

[0035]2 service brake piston

[0036]3 service brake pressure changer

[0037]4 connection

[0038]5 piston rod

[0039]6 return spring

[0040]7 adjusting device

[0041]8 spring piston

[0042]9 accumulator-type spring

[0043]10 spring pressure chamber

[0044]11 connection

[0045]12 threaded screw drive

[0046]13 latch

[0047]14 screw

[0048]15 plastic bush

[0049]16 nut

[0050]17 torque lock

[0051]18 gear wheel element

[0052]19 sliding surface

[0053]20 spring

[0054]21 grip

[0055]22 detent flank 

1. Spring brake cylinder having an emergency release device, particularly for rail vehicles, and having a spring piston (8) which can be moved axially within a housing (1) and which, on the one hand, can be moved by means of an accumulator-type spring (9) for operating the brake in the event of a pressure drop and, on the other hand, can be moved by a spring pressure chamber (10), which can be acted upon by a pressure medium, for releasing this spring brake, as well as having a normally locked, not self-locking threaded screw drive (12) which is arranged in the flux of force between the spring piston (8) and an output-side piston rod (5) and which can be manually unlocked by way of a latch (13) assigned to the emergency release device, in order to be able to release the spring brake without any pressure medium, characterized in that an outer-radial sliding surface (19) for the latch (13) held in contact thereon is assigned to the part of the threaded screw drive (12) which is rotatable relative to the housing (1), on which sliding surface (19) only a detent flank (22) interacting in a form-locking manner with the latch (13) is constructed for locking the emergency release device, the pitch of the threaded screw drive (12) being dimensioned such that the rotatable part of the threaded screw drive (12) carries out less than a complete rotation along its maximal axial adjusting stroke.
 2. Spring brake cylinder according to claim 1, characterized in that the sliding surface (19) of the part of the threaded screw drive (12) rotatable relative to the housing (1) is constructed in the manner of a curved path.
 3. Spring brake cylinder according to claim 2, characterized in that the detent flank (22) constructed on the curved-path-type sliding surface (19) is an essentially radially aligned surface.
 4. Spring brake cylinder according to claim 2, characterized in that the switching condition of the emergency release device can be indicated by way of the stroke difference of the latch (13) resulting from the curved-path-shaped sliding surface (19).
 5. Spring brake cylinder according to claim 1 or 2, characterized in that the detent flank (22) constructed on the sliding surface (19) is shaped in a groove-type manner as an indentation or is shaped in a tooth-type manner as an elevation.
 6. Spring brake cylinder according to claim 1, characterized in that the part of the threaded screw drive (12) which is rotatable relative to the housing (1) is constructed as a screw (14) which is axially displaceable together with the piston rod (5) and which is disposed to be rotatable about the piston rod (5), and which interacts with a nut (16), as a non-rotatable part of the threaded screw drive (12), which is stationarily arranged with respect to the spring piston (8).
 7. Spring brake cylinder according to claim 6, characterized in that a gear wheel element (18) is stationarily fastened to the screw (14), which gear wheel element (18) has the outer-radial sliding surface (19) with the detent flank (22) for the latch (13) interacting herewith for forming the emergency release device.
 8. Spring brake cylinder according to claim 6 or 7, characterized in that the screw (14) can be displaced by way of an outer-radial plastic bush (15) and is rotatably guided in the housing (1).
 9. Spring brake cylinder according to claim 1, characterized in that the part of the threaded screw drive which is rotatable relative to the housing is constructed as a nut which can be axially displaced together with the spring piston and which is disposed to be coaxially rotatable on the spring piston, and which interacts with a screw, as a non-rotatable part of the threaded screw drive, which is stationarily arranged with respect to the piston rod.
 10. Spring brake cylinder according to one of the preceding claims, characterized in that a spring (20) is provided which is arranged between the latch (13) and the housing (1) and which is constructed in the manner of a compression or tension spring and holds the latch (13) in a continuous contact on the sliding surface (19) of the rotatable part of the threaded screw drive (12).
 11. Spring brake cylinder according to one of the preceding claims, characterized in that the latch (13) can be remote-controlled by means of an auxiliary device. 